In a gas turbine engine or any type of turbomachine a rotor is provided to particularly rotate compressor blades and/or turbine blades about an axis. To allow this rotation the rotor will be connected to a stator via bearings. These bearings may be lubricated by lube oil provided from an oil tank.
Lube oil from the bearing may be guided back to the oil tank via one or more drain pipes. There may be limited space within the core of the gas turbine engine or the turbomachine through which the drain pipe must be routed. The areas directly surrounding these drain pipes may have different temperatures along the length of the drain pipes, as a casing of the gas turbine engine or the turbomachine will experience typically higher temperatures than the ambient temperature surrounding the gas turbine engine. This is due to the fact that a working fluid will be heated by combustors and that air extracted from a compressor even though probably extracted for cooling a hot turbine region may also have an increased temperature level.
After a longer period of operation in conventional designs in an interior of the drain pipes a carbonised layer may be formed. This may be experienced as the drained lube oil may be overheating due to the mentioned temperature effects.
As a result, lubrication characteristics of the oil are deteriorated. And even further, flakes of the carbonised layer can possibly break loose and block oil filters requiring additional maintenance.